US20240069573A1

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Publication number: US20240069573A1
Application number: US18/454,552
Authority: US
Inventors: Alexis Anthony LIBERSON
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2022-08-24
Filing date: 2023-08-23
Publication date: 2024-02-29
Also published as: GB2621982A; GB202212320D0; EP4328131A1

Abstract

An aircraft attitude controller configured to obtain information representative of an attitude of an aircraft is disclosed. On the basis of the information, the attitude controller is configured to control the attitude of the aircraft by actively controlling a position of a winglet at a distal end of a wing portion of a wing of the aircraft, relative to the wing portion, thereby to control an angle of incidence of the winglet.

Description

TECHNICAL FIELD

The present invention relates to aircraft attitude controllers, wing systems and aircraft comprising such aircraft attitude controllers and wing systems.

BACKGROUND

The mass of an aircraft typically decreases throughout a flight of the aircraft as fuel is consumed to power engines of the aircraft. Such a reduction in mass, particularly during a cruise phase of a flight of the aircraft, may reduce a lift requirement of the aircraft. An attitude, such as a pitch of the aircraft, may therefore change throughout the flight to achieve the amount of lift required.

In addition, fuel tanks are typically distributed throughout an aircraft, such as within wings of the aircraft. Therefore, a distribution of mass in the aircraft may also vary throughout a flight of an aircraft. This may, in turn, affect a centre of gravity of the aircraft. This may similarly cause a change in attitude of the aircraft, as the centre of gravity may move relative to a centre of lift of the aircraft.

In some aircraft, fuel may be used as a ballast to adjust the centre of gravity of the aircraft, thereby to control an attitude of the aircraft. For example, fuel may be passed between tanks that are located fore and aft of the aircraft, such as between a tank located substantially centrally in the aircraft and a tank located towards a tail of the aircraft. This may require the use of pumps, pipes, and other ancillary equipment.

SUMMARY

A first aspect of the present invention provides an aircraft attitude controller configured to: obtain information representative of an attitude of an aircraft; and, on the basis of the information, control the attitude of the aircraft by actively controlling a position of a winglet at a distal end of a wing portion of a wing of the aircraft, relative to the wing portion, thereby to control an angle of incidence of the winglet.

Controlling the attitude of the aircraft may reduce a drag of the aircraft, reduce a fuel consumption of the aircraft, and/or increase an efficiency of the aircraft. This may be particularly advantageous when an attitude of the aircraft changes during a flight, such as due to a changing mass and/or changing distribution of mass of the aircraft. For instance, as fuel is spent during a flight of the aircraft, a mass of the fuel and/or distribution of the fuel in the aircraft may change. This may cause a centre of gravity of the aircraft to change, which may in turn result in a change in the attitude of the aircraft. A change in the attitude of the aircraft may result in an increase in a drag or fuel consumption of the aircraft. Additionally, a reduction in a mass of the aircraft may result in a lower lift requirement of the aircraft, which may in turn result in a change in an attitude of the aircraft to achieve the required lift.

Controlling the position of the winglet to control the angle of incidence of the winglet may change a distribution of lift on the wing, for example to control a centre of lift of the aircraft and thereby control an attitude of the aircraft. In this way, the winglet may be moved to adjust a centre of lift of the aircraft as a centre of gravity of the aircraft and/or as the lift requirements of the aircraft change during a flight. This may allow the aircraft to fly at an attitude that is beneficial, and in particular at an attitude at which a level of drag, such as a lift-induced drag (or “induced drag”) and/or a drag associated with a fuselage of the aircraft, is lower than it would otherwise be in the absence of such control. This may also allow an attitude of the aircraft to be adjusted without moving fuel to different tanks in the aircraft, such as without moving fuel back and forth along a longitudinal axis of the aircraft to change the centre of gravity of the aircraft. In particular, there may be no requirement for a fuel ballast system in the aircraft. This may reduce a cost, weight, and/or complexity of the aircraft.

Optionally, the aircraft attitude controller is configured to obtain the information representative of the attitude of the aircraft, and to control the attitude of the aircraft, during a cruise phase of a flight of the aircraft. This may be particularly advantageous as an aircraft typically spends most of a flight in the cruise phase. Reducing drag during the cruise phase may therefore present a significant improvement in fuel consumption. Moreover, a large portion of the fuel of the aircraft is typically consumed during a cruise phase, and so a mass and/or a distribution of mass, and therefore an attitude, of the aircraft may change significantly throughout a cruise phase. In this way, the controller may be configured to control the attitude of the aircraft as the mass and/or distribution of mass changes throughout the cruise phase, in particular by controlling the position of the winglet throughout the cruise phase.

The controlling the position of the winglet may also advantageously change a level of induced drag generated by the wing and/or the wing portion, such as by controlling a distribution of lift over a span of the wing, and/or by controlling a tip vortex generated at the tip of the wing and/or winglet. This may allow the controller to control a level of induced drag during a flight, such as during the cruise phase, for instance to reduce the level of induced drag. Optionally, the controlling the attitude of the aircraft may be to reduce a fuel consumption of the aircraft and may comprise balancing a change in induced drag caused by a change in the position of the winglet with a reduction in other forms of drag, such as fuselage drag, caused by a change in the attitude of the aircraft. Moreover, the attitude of the aircraft may be controlled without operating other control surfaces of the aircraft. This may be beneficial in that operation of other control surfaces may lead to an increase in drag that is greater than would arise from controlling the position of the winglet. Indeed, as noted above, controlling the position of the winglet may even reduce a level of induced drag on the aircraft.

Optionally, the controller may be configured to control the position of the winglet during a take-off and/or a landing procedure, such as to increase or decrease an angle of attack of the winglet relative to a streamwise airflow over the wing. This may change an amount of lift generated by the winglet, such as to increase a lift of the entire wing during the take-off and/or landing procedure. Alternatively, or in addition, controlling the position of the winglet may control, such as reduce or prevent, a separation of airflow over the winglet during the take-off and/or landing procedure. This may, in turn, increase a lift and/or reduce a drag on the aircraft and/or wing system, in use. This may allow the aircraft to take-off and/or land at lower speeds, and as such may also reduce a landing distance of the aircraft. This may allow the aircraft to take off and/or land on shorter runways than it may otherwise be able to.

Optionally, the attitude of the aircraft comprises a pitch of the aircraft and/or an angle of attack of the aircraft. The pitch may be a pitch of a longitudinal axis of the aircraft. As noted above, as fuel is spent during a flight, such as during cruise of the aircraft, a centre of gravity of the aircraft may change. For example, if the aircraft comprises plural fuel tanks, or fuel tank portions, spaced apart longitudinally in the aircraft, such as in a fuselage and/or wing of the aircraft, then fuel may move fore and aft of the aircraft during flight. This may, in turn, cause a centre of gravity of the aircraft to move fore and aft of the aircraft. If the centre of lift of the aircraft remains relatively unchanged, or if it does not change in tandem with the centre of gravity, then the change in the centre of gravity may lead to a change in the pitch of the aircraft. A change in a pitch of the aircraft may cause a greater area of the fuselage to be exposed to a streamwise airflow (relative to the aircraft) over the fuselage, thereby increasing a drag of the fuselage of the aircraft. For instance, if the aircraft is pitched upwards, the streamwise airflow may impinge on a belly of the fuselage, and if the aircraft is pitched downwards, then the streamwise airflow may impinge on a top of the fuselage.

By controlling the position of the winglet, a location of the centre of lift of the wing in a longitudinal direction of the aircraft may be changed, such as to compensate for the change in the centre of gravity of the aircraft and thereby control the attitude, such as the pitch, of the aircraft. This may be to facilitate maintenance of the aircraft at a pitch whereby a longitudinal axis of the aircraft is substantially aligned with a direction of travel of the aircraft, thereby to reduce, or minimise, drag associated with the fuselage of the aircraft.

Optionally, the information comprises information on any one or more of the following properties: a pitch of the aircraft; an angle of attack of the aircraft; a speed of the aircraft; a drag of the aircraft; a mass of the aircraft; a distribution of mass of the aircraft; a centre of gravity of the aircraft; an amount of fuel in the aircraft; a fuel consumption of the aircraft; and an efficiency of the aircraft.

In other words, the controller may control the attitude of the aircraft based on any one or more of the above properties, such as based on an amount of, or distribution of, mass and/or fuel in the aircraft, based on a fuel consumption of the aircraft, and/or based on an efficiency of the aircraft. In this way, the controller may control the attitude of the aircraft to influence or control one or more of the properties listed above. For instance, the controller may be configured to control the attitude of the aircraft to reduce, or minimise, a fuel consumption of the aircraft, and/or to increase an efficiency of the aircraft. Alternatively, the controller may detect a pitch and/or an angle of attack of the aircraft, and control the attitude, such as the pitch of the aircraft, based on the detected pitch and/or angle of attack. A speed of the aircraft may affect a lift generated by wings of the aircraft, which may, in turn, affect an attitude of the aircraft. The controller may control the attitude of the aircraft based on the speed of the aircraft, for instance so that the aircraft can fly at a desired speed for a given attitude, or at a desired attitude for a given speed.

Optionally, the controller is configured to control the attitude of the aircraft so as to bring one or more of the above listed properties towards a respective target value. For instance, the controller may be configured to control the attitude of the aircraft to facilitate maintenance of a target fuel consumption, target efficiency, and/or a target drag of the aircraft.

Optionally, the aircraft attitude controller is configured to determine a target attitude of the aircraft. Optionally, the controlling the attitude of the aircraft comprises controlling the attitude of the aircraft to bring the attitude of the aircraft towards the target attitude of the aircraft.

The target attitude may be an attitude at which the information representative of the attitude of the aircraft, such as any one or more of the above listed properties, reaches, or approaches, a respective target value. Alternatively, or in addition, the target attitude may be predetermined, and/or may be based on a theoretical attitude at which a property (such as fuel consumption, efficiency, and/or drag of the aircraft) is improved or optimised. The target attitude may be determined based on a mass of the aircraft and/or a distribution of mass in the aircraft. For instance, the target attitude may change as a mass, and therefore lift requirement, of the aircraft changes during a flight. A fully-loaded aircraft may, for example, be flown at an increased target pitch in order to generate sufficient lift. As fuel is spent, the lift requirements of the aircraft may reduce, and so the target pitch may be reduced.

A second aspect of the present invention provides a wing system for an aircraft, the wing system comprising at least a wing portion of a wing, a winglet at a distal end of the wing portion, and a controller, wherein a position of the winglet relative to the wing portion is variable to change an angle of incidence of the winglet, and wherein the controller is configured to obtain information representative of an attitude of an aircraft, and, on the basis of the information, to control the attitude of the aircraft by actively controlling the position of the winglet relative to the wing portion.

As with the aircraft attitude controller of the first aspect, by providing a controller configured to control the attitude of the aircraft by controlling the position of the winglet to change the angle of incidence of the winglet, the wing system may improve an efficiency of the aircraft and/or reduce a drag and/or fuel consumption of the aircraft.

The wing portion may comprise an inboard portion of the wing, such as a portion of the wing connected to a fuselage of the aircraft, and/or may comprise an outboard portion of the wing. The wing portion may be orientated at a fixed angle of incidence relative to a longitudinal axis of the aircraft, such as an axis aligned with the fuselage of the aircraft. The wing portion and/or the wing may comprise twist, meaning that an angle of incidence of the wing and/or wing portion may vary along a span of the wing and/or wing portion. The twist of the wing portion may be fixed. By controlling the position of the winglet relative to the wing portion to change the angle of incidence of the winglet, an overall twist of the wing may be adjusted. This may change a distribution of lift over the wing, such as a spanwise and/or a streamwise distribution of lift, which may in turn cause a change in the attitude of the aircraft.

Optionally, the winglet is rotatably movable relative to the wing portion. In this way, the position of the winglet may be an angular position of the winglet relative to the wing portion.

Optionally, the wing tip is rotatably movable about an axis of rotation that is nonorthogonal to a vertical plane that includes a longitudinal axis of the aircraft. In this way, movement of the wing tip about the axis of rotation may vary a cant angle of the winglet relative to a wing plane of the wing portion. The wing plane may be aligned with a horizontal plane that includes the longitudinal axis of the aircraft, or may itself be at an angle to such a horizontal plane. The wing plane may be aligned with a span and/or a chord of the wing portion, such as a chord at a distal end of the wing portion.

The winglet may be rotatable to vary the cant angle of the winglet above and/or below the wing plane. The winglet may be rotatable to vary the cant angle in a range of up to 5 degrees, up to 10 degrees, up to 25 degrees, up to 45 degrees, up to 90 degrees, or greater than 90 degrees at one or both sides of the wing plane. In this way, the winglet may be rotatable to vary the cant angle so that the winglet is substantially perpendicular to the wing plane and/or the horizontal plane. This may represent a “stowed” position of the winglet. This may allow a total wingspan of the wing system and/or an aircraft comprising the wing system to be reduced, such as when the aircraft is performing ground manoeuvres and/or when the aircraft is in proximity to a terminal of an airport, where space may be restricted. Optionally, the winglet is rotatable to vary the cant angle to different extents above and below the wing plane.

Optionally, an axis of rotation of the winglet relative to the wing portion is orientated at a non-zero toe angle to a vertical plane that includes a longitudinal axis of the aircraft. Optionally, the toe angle is up to 5, up to 10, up to 20, up to 30, up to 45, or greater than 45 degrees. For instance, the toe angle may be from 25 degrees to 35 degrees, such as 30 degrees.

By providing the non-zero toe angle, movement of the winglet about the axis of rotation may vary the angle of incidence of the winglet. This may lead to a change in the twist of the wing portion. As discussed above, by changing the angle incidence of the winglet, a centre of lift of the wing portion, or the wing comprising the wing portion, may be moved fore and/or aft of the aircraft, thereby to change a centre of lift of the aircraft. This may allow the attitude of the aircraft to be controlled, such as to reduce a drag of the aircraft and/or improve a fuel efficiency of the aircraft during a flight of the aircraft.

The wing portion may be a wing portion of a swept wing. For instance, the wing portion may be orientated so that a span line of the wing portion is at a sweep angle to a frontal plane that is orthogonal to a longitudinal axis of the aircraft. In that case, the axis of rotation of the winglet may be perpendicular to the span line of the wing portion. This may improve an ease of construction of the winglet and/or a mechanism for controlling the position of the winglet. Moreover, movement of the winglet to increase or decrease an angle of incidence of the winglet may increase or decrease an amount of lift provided by the winglet. This change in lift would act at the end of the wing portion. As such, by providing a swept wing portion, the change in lift may change a longitudinal distribution of lift on the wing. For instance, reducing an amount of lift provided by the winglet at the tip of the wing portion may move a centre of lift provided by the wing portion forward relative to a longitudinal axis of the aircraft.

Optionally, the wing system comprises a restrictor operable to restrict a range of movement of the winglet. Optionally, the controller is configured to selectively engage or disengage the restrictor. In this way, when the restrictor is engaged, the range of movement of the winglet is restricted by the restrictor, and when the restrictor is disengaged, the range of movement of the winglet is not restricted by the restrictor. The controller may be configured to engage the restrictor during a flight of the aircraft, such as to permit the position of the winglet to be varied within a restricted range during the flight. The flight may include a take-off and landing procedure of the aircraft, as well as a cruise phase of the aircraft. By restricting the range of movement of the winglet during the flight, aerodynamic loads on the winglet and/or loads on a mechanism for controlling movement of the winglet, during the flight, may be reduced. This may also prevent the winglet from being inadvertently moved to a position that may be detrimental to a flight of the aircraft, such as preventing movement of the winglet to a stowed position as described above. In such a stowed position, an angle of incidence of the winglet may be significantly reduced compared to an angle of incidence when the winglet is positioned at an extreme of the restricted range of movement provided by the restrictor. This may cause a similarly significant increase in drag on the winglet and/or an undesirable change in the lift distribution over the wing.

The controller may be configured to disengage the restrictor when the aircraft is on the ground, such as when the aircraft is performing ground manoeuvres and/or when the aircraft is in proximity to a terminal of the aircraft. In this way, the winglet may be moved to the stowed position described above when the aircraft is on the ground. In the stowed position, the winglet may be substantially vertical, such that a span of the winglet is substantially parallel to a vertical plane including a longitudinal axis of the aircraft. In this way, a wingspan of the aircraft comprising the wing system, and/or an aspect ratio of the wing of the aircraft, may be reduced when the winglet is stowed. This may allow the aircraft to operate on the ground at airports having reduced manoeuvring space and/or at airports that place upper limits on a wingspan of an aircraft, while allowing a greater wingspan to be employed in flight, such as to reduce a drag of the aircraft, such as an induced drag of the aircraft.

Optionally, the restrictor comprises a body that is fixed to the wing portion and a slot within which a portion of the winglet, such as a protrusion on the winglet, is configured to move. The slot may have a fixed dimension along which the portion of the winglet can move, such as when the position of the winglet is controlled or varied, thereby restricting a range of movement of the winglet. The restrictor may be releasable from the portion of the winglet to disengage the restrictor. This may be by the body being movable relative to the winglet and the wing portion, and/or by the portion of the winglet being movable relative to the body and/or the slot. Alternatively, the restrictor may be configured to restrict a range of movement of the winglet in any other suitable way. Optionally, a level of restriction of movement of the winglet provided by the restrictor is variable. This may be by the slot comprising a variable dimension along which the portion of the winglet is movable. It will be understood that the level of restriction provided by the restrictor may be varied in any other suitable way.

Optionally, the winglet is movable to an extended position, in which a proximal end of the winglet is substantially aligned with a distal end of the wing portion. Optionally, in the extended position, an upper surface of the winglet is substantially aligned with an upper surface of the wing portion. In this way, an upper and/or a lower surface of the winglet may form a smooth aerodynamic transition between a respective upper and/or lower surface of the wing portion in the extended position.

Optionally, a span of the winglet, when the winglet is in the extended position, constitutes from 10% to 50% of the total span of the wing comprising the wing portion. Optionally, the span of the winglet, when the winglet is in the extended position, constitutes up to 15%, up to 20%, up to 25%, or from 25% to 50% of the total span of the wing comprising the wing portion. Increasing a proportion of the span of the wing that is formed by the winglet may increase an authority of the winglet over a distribution of lift on the wing. For example, moving a larger winglet may increase a level of twist of the wing to a greater extent than correspondingly moving a smaller winglet would. Moreover, a change in a lift generated by a larger winglet, caused by movement of the winglet, may be greater than a change in lift caused by corresponding movement of a smaller winglet. Thus, particularly when the wing portion is a swept wing portion, such as a wing portion of a swept wing, movement of a larger winglet may cause a greater variation in a longitudinal position of a centre of lift of the aircraft than corresponding movement of a smaller winglet would.

Optionally, the wing system comprises an actuator for varying the position of the winglet relative to the wing portion. In this way, the controller may be configured to control the position of the winglet by causing operation of the actuator. In this way, the controller may actively control the position of the winglet using the actuator, such as to actively position the winglet in any position within a range of movement of the winglet. This may improve a versatility of the wing system and/or may improve an authority of the wing system over an attitude of the aircraft, such as to allow more precise control of the attitude of the aircraft.

The actuator may comprise a hydraulic actuator. Alternatively, or in addition, the actuator may comprise an electric or electromechanical actuator, such as an electric motor and/or an electrically operated piston. Providing an electric or electromechanical actuator may reduce a weight of the aircraft wing system, such as by not requiring pipework and/or hydraulic fluid.

Optionally, the controller is the aircraft attitude controller of the first aspect. The controller of the wing system may comprise any of the optional features of the aircraft attitude controller of the first aspect.

A third aspect of the present invention provides a method of controlling an attitude of an aircraft, the method comprising: obtaining information representative of the attitude of the aircraft; and, on the basis of the information, controlling the attitude of the aircraft by controlling a position of a winglet at a distal end of a wing portion of a wing of the aircraft, relative to the wing portion, thereby to control an angle of incidence of the winglet.

As with the aircraft attitude controller of the first aspect and the wing system of the second aspect, by controlling the attitude of the aircraft by controlling the position of the winglet to change the angle of incidence of the winglet, the method may improve an efficiency of the aircraft and/or reduce a drag and/or fuel consumption of the aircraft.

Optionally, the method comprises determining a target attitude of the aircraft, wherein the controlling the attitude of the aircraft comprises controlling the attitude of the aircraft to bring the attitude of the aircraft towards the target attitude of the aircraft.

The method may comprise any of the optional actions performed by the aircraft attitude controller of the first aspect or the controller of the wing system of the second aspect. As such, the method may comprise any of the optional features ascribed to the aircraft attitude controller of the first aspect or the controller of the wing system of the second aspect.

It will be appreciated that the controlling the position of the winglet may comprise controlling the position of the winglet of the wing system of the second aspect of the present invention. As such, the winglet and/or the wing system may comprise any of the optional features of the wing system of the second aspect.

A fourth aspect of the present invention provides a non-transitory computer-readable storage medium storing instructions that, when executed by a processor, cause the processor to perform the method of the third aspect of the present invention. The processor may be a processor of the aircraft attitude controller of the first aspect or a processor of the controller of the wing system of the second aspect, for example. The aircraft attitude controller of the first aspect and/or the wing system of the second aspect may comprise the non-transitory computer-readable storage medium.

A fifth aspect of the present invention provides an aircraft comprising the controller of the first aspect, the wing system of the second aspect, and/or the non-transitory computer-readable storage medium of the fourth aspect. The aircraft may benefit from any of the optional features and/or advantages ascribed to the aircraft attitude controller of the first aspect, the wing system of the second aspect, the method of the third aspect and/or the non-transitory computer-readable storage medium of the fourth aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIGS.1A and1B show respective isometric and top-down schematic views of an aircraft;

FIG.2 shows a top-down schematic view of a wing system of the aircraft ofFIG.1;

FIGS.3A and3B show schematic views towards a leading edge of a winglet of the wing system ofFIG.2, illustrating a deflection of a winglet;

FIG.4 shows an end-on schematic view along a span of the winglet at the deflections shown inFIGS.3A and3B;

FIG.5 shows a schematic view towards the leading edge of the winglet, illustrating the winglet in a stowed position;

FIG.6 shows a schematic view towards the leading edge of the winglet, showing a restrictor of the wing system;

FIG.7 shows a flow chart of a method of controlling an attitude of the aircraft ofFIG.1; and

FIG.8 shows a non-transitory computer-readable storage medium according to an example.

DETAILED DESCRIPTION

FIG.1A shows an isometric view of anexample aircraft1 comprising afuselage10 and a pair of wings (herein referred to singly or jointly with the reference numeral11). Thefuselage10 extends generally along alongitudinal axis15 of theaircraft1. Here, thelongitudinal axis15 is a direction of minimum aerodynamic drag of thefuselage10. In other examples, thelongitudinal axis15 is a geometric centreline through the fuselage, which may be different to the direction of minimum aerodynamic drag.FIG.1B shows a top-down schematic view along avertical axis16 of theaircraft1. Thewings11 each extend in a direction oblique to ahorizontal axis17 of theaircraft1. In other words, thewings11 are sweptwings11, which are here swept at an angle of 30° from thehorizontal axis17, but may be swept at any other suitable angle. It will be appreciated thatother example aircraft1 may comprise unswept wings, which extend substantially parallel to thehorizontal axis17.

Theaircraft1 also comprises awing system100. Thewing system100, as better shown inFIG.2, comprises awing portion110 of awing11 of theaircraft1 and awinglet120 at adistal end112 of thewing portion110. While thepresent wing system100 is described in relation to awing portion110 of asingle wing11 of theaircraft1, it will be understood that thewing portion110 may be awing portion110 of eitherwing11 of theaircraft1. In other examples, anentire wing11 may be considered thewing portion110.

Thewinglet120 is movable relative to thewing portion110. Specifically, thewinglet120 is rotatably connected to thewing portion110, so that the winglet is rotatably movable relative to thewing portion110. An axis ofrotation123 of thewinglet120 relative to thewing portion110 is oriented at a non-zero toe angle n to a vertical plane that includes thelongitudinal axis15 of theaircraft1. In the present example, a sweep angle of thewing11 and/or thewing portion110 relative to a frontal plane that is orthogonal to thelongitudinal axis15 is 30°, and the axis ofrotation123 is perpendicular to aspan line113 of thewing portion110. Thespan line113 is here parallel to aleading edge114 of thewing portion110. As such, the axis ofrotation123 is orientated a toe angle of 30°. In other examples, the wing sweep and/or the toe angle may be any other suitable value. For instance, the axis ofrotation123 may be non-perpendicular to thespan line113. In other examples, thespan line113 is any other suitable dimension of a wingspan of thewing portion110. In some such examples, the axis ofrotation123 is perpendicular to theleading edge114 of thewing portion110, but this need not be the case.

A position of thewinglet120 is thereby variable, relative to thewing portion110, by rotating thewinglet120 around the axis ofrotation123. Movement of thewinglet120 about the axis ofrotation123 causes a cant angle α of the wing relative to awing plane114 of thewing portion110 to be varied. Thewing plane114 in the present example comprises a span and a chord of thewing portion110, and in particular a chord at the distal end12 of thewing portion110. In other examples, thewing plane114 may comprise an average chord of thewing portion110. Alternatively, thewing plane114 may be defined in any other suitable way. In some examples, the cant angle α is defined relative to a horizontal plane that is orthogonal to thevertical axis16 of theaircraft1. In some examples, thewing plane114 is substantially aligned with the horizontal plane.

FIGS.3A and3B show an example of thewinglet120 at different positions relative to thewing portion110. In particular, thewinglet120 shown using dashed lines in each ofFIGS.3A and3B is in an extended position, labelled “Z”, in which aproximal end122aof thewinglet120, i.e., an end of thewinglet120 closest to thefuselage10, is aligned with thedistal end112 of thewing portion110, i.e., an end of thewing portion110 farthest away from thefuselage10. This represents a cant angle α of zero. In the extended position, upper and

lower surfaces

121a,121bof the winglet form a smooth aerodynamic transition with respective upper and

lower surfaces

111a,111bof the wing portion. That is, in the extended position Z, theupper surface121aof thewinglet120 is substantially aligned with theupper surface111aof thewing portion110, and thelower surface121bof thewinglet120 is substantially aligned with thelower surface111bof thewing portion110. In the present example, a distance between the upper and

lower surfaces

121a,121bof thewinglet120, such as an average distance along a chord of thewinglet120, decreases from theproximal end122ato adistal end122bof thewinglet120. In other examples, this may not be the case. For instance, the average distance between the upper and

lower surfaces

121a,121bof thewinglet120 may be substantially constant from theproximal end122ato thedistal end122bof thewinglet120.

Thewinglet120 shown using solid lines inFIG.3A is in an upwardly deflected position, labelled position “A”, so that the winglet extends above thewing plane114. That is, in the first deflected position, thewinglet120 is positioned so as to have a positive cant angle α. Thewinglet120 shown using solid lines inFIG.3B is in a downwardly deflected position, labelled position “B”, so that the winglet extends below thewing plane114. Because the axis ofrotation123 of thewinglet120 is at a non-zero toe angle η, deflection of thewinglet120 causes a change in an angle of incidence θ of thewinglet120. This is best seen inFIG.4, which shows a schematic end-on view of thewinglet120 along a span of thewinglet120. Specifically, deflection of thewinglet120 upwardly, such as towards position A, causes a reduction in an angle of incidence θ of thewinglet120. Deflection of thewinglet120 downwardly, such as towards position B, causes an increase in the angle of incidence θ of thewinglet120. The angle of incidence θ of thewinglet120 is here defined as an angle of a chord of thewinglet120, such as a chord at theproximal end122aor thedistal end122bof thewinglet120, or an average chord along a span of thewinglet120, to thelongitudinal axis15 of theaircraft1. However, it will be appreciated that the angle of incidence θ may be defined in any other suitable way as will be evident to the skilled person. For instance, the angle of incidence θ of thewinglet120 may be defined relative to an angle of incidence of thewing portion110.

In the example shown inFIG.4, the angle of incidence θ of thewinglet120 in the extended position Z (and therefore the angle of incidence of thedistal end112 of the wing portion110) is substantially zero. In many examples, the angle of incidence of thewing11,wing portion110 and thewinglet120 in the extended position Z, is non-zero. In some examples, thewing11 and/or thewing portion110 comprises twist, in which an angle of incidence of thewing11 and/or thewing portion110 changes along a span of thewing11 and/or thewing portion110. In any case, deflection of thewinglet120 so as to change the angle of incidence θ of thewinglet120 causes a change in an effective twist of thewing system100 comprising thewing portion110 and thewinglet120, and/or of thewing11 comprising thewing system100. That is, increasing and decreasing a level deflection of thewinglet120 increases and decreases an effective twist of thewing11 and or thewing system100 of theaircraft1. This, in turn, causes a change in a distribution of lift over thewing11 and/or thewing system100.

In some examples, changing a distribution of lift over thewing11 and/or thewing system100 by deflecting thewinglet120 causes a change in a centre oflift14 of theaircraft1. For instance, as thewings11 of theaircraft1 are swept backwards, lift generated by thewinglet120 acts at a rearward end of thewing11 and/orwing portion110, while lift generated thewing11 orwing portion110 closer to thefuselage10 acts at a forward end of thewing11. As such, a decrease in an amount of lift generated at the winglet, such as by deflecting thewinglet120 upwards to decrease the angle of incidence θ of thewinglet120, and therefore an angle of attack of thewinglet120 relative to a free stream air flow over thewinglet120, may act to move the centre oflift14 forward. To the contrary, an increase in an amount of lift generated by thewinglet120, such as by deflecting thewinglet120 downwards to increase the angle of incidence θ, and therefore angle of attack, of thewinglet120, may act to move the centre oflift14 rearwardly. Moreover, adjusting the position of thewinglet120 may adjust a level of lift-induced drag (or “induced drag”) of thewing system100 and/or thewing11. For instance, deflecting thewinglet120 upwards may reduce a level of aerodynamic drag associated with wing tip vortices, and thereby change a lift distribution over the wing, which could also affect the centre oflift14. This may, in turn affect an attitude of theaircraft1, such as a pitch of theaircraft1. In other words, an attitude of theaircraft1. In other words, an attitude of theaircraft1 may be controlled by controlling a position of thewinglet120.

It will be appreciated that increasing the toe angle η of the axis ofrotation123 of thewinglet120 would increase a change in the angle of incidence θ of thewinglet120 for a given deflection of thewinglet120. This would, in turn, increase an amount of effective twist imparted to thewing11 and/orwing system100 for the given deflection of thewinglet120. It will also be appreciated that increasing a size, such as a span and/or area, of thewinglet120 relative to thewing11 and/or thewing portion110 would increase an amount of effective twist imparted by a given deflection of thewinglet120. Thus, increasing the toe angle η and/or the size of thewinglet120 may increase an authority of thewinglet120 over the lift distribution over thewing11 and/orwing system100, and as such may increase an authority of thewinglet120 over the attitude of theaircraft1. In the present example, when thewinglet120 is in the extended position Z, a span of thewinglet120 makes up around 25% of a total span of thewing11; however, it will be appreciated that thewinglet120 may be of any other suitable size.

As shown inFIG.5, thewinglet120 is movable to a stowed position S, in which thewinglet120 is substantially vertical, such that a span of thewinglet120 is substantially parallel to thevertical axis16. In the stowed position S, a total wingspan of thewing system100 and/or theaircraft1 is reduced. The reduction in span may be most significant when thewinglet120 has a larger span. For instance, when thewinglet120 has a span that constitutes 25% of a span of thewing11 when thewinglet120 is in the extended position Z, a length of thewing11 may be reduced by up to 25% by moving thewinglet120 to the stowed position S. This can allow thewings11 of theaircraft1 to have a large aspect ratio when thewinglet120 is deployed, such as when the winglet is in the extended position Z or a deflected position A, B, while still allowing theaircraft1 to perform ground manoeuvres at smaller airports having restricted space. A larger aspect ratio may reduce a drag of theaircraft1 when in flight. Moreover, larger wings may allow more lift to be generated at lower speeds, thereby reducing a landing distance of theaircraft1 and permitting theaircraft1 to land and/or take-off on smaller runways.

In the present example, thewinglet120 comprises acontroller150 configured to perform amethod700 of controlling an attitude of theaircraft1. Themethod700 is shown schematically inFIG.7. Thecontroller150 may be located in any suitable location on theaircraft1. Thecontroller150 is configured to obtain720 information representative of an attitude of theaircraft1, in particular during a flight of theaircraft1. Thecontroller150 is configured to control740 the attitude of theaircraft1, on the basis of the information, by actively controlling741 a position of thewinglet120. As discussed above, actively controlling741 the position of thewinglet120 is to control an angle of incidence of thewinglet120, which in turn can vary a lift distribution over thewing11 of theaircraft1, and thereby control the attitude of theaircraft1.

In order to actively control740 the attitude of the aircraft, thewing system100 comprises anactuator125 configured to position thewinglet120 in any position within a range of movement of thewinglet120 around the axis ofrotation123. Theactuator125 here comprises an electric actuator, specifically an electric motor. It will, however, be appreciated that any othersuitable actuator125 may be used. For instance, theactuator125 may comprise a hydraulic actuator, or an electromechanical actuator, such as a hydraulically or electrically operated piston. Thecontroller150 is configured to control theactuator125 to control the position of thewinglet120.

Theaircraft1 also comprises asensor system160, which in this example is a part of thewing system100, comprising sensors configured to sense the information representative of the attitude of theaircraft1. That is, in the present example, thecontroller150 is configured to obtain720 the information based on data received from thesensory system160. In other examples, thecontroller150 is configured to obtain720 some or all of the information from one or more other sensors and/or controllers of theaircraft1 and/or thewing system100. The information obtained by thecontroller150, in various examples, comprises information on any one or more of the following properties: a pitch of theaircraft1; an angle of attack of theaircraft1; a speed of theaircraft1; a drag of theaircraft1; a mass of theaircraft1; a distribution of mass in theaircraft1; a centre ofgravity13 of theaircraft1; an amount of fuel in theaircraft1; a fuel consumption of theaircraft1; and an efficiency of theaircraft1, such as an efficiency of one or more engines of theaircraft1. It will be appreciated that the above listed properties may be sensed and/or determined in any suitable way. For instance, thesensory system160 may comprise a fuel flow sensor, and/or a fuel level detector for detecting a fuel consumption of theaircraft1. Alternatively, or in addition, thesensory system160 may comprise an attitude sensor, such as a gyroscope or any other suitable sensor, for detecting the attitude, such as the pitch of the aircraft, and/or a speed sensor for determining a speed of theaircraft1.

Thecontroller150 of the present example is configured to determine720 a target attitude of theaircraft1, specifically a target pitch of theaircraft1. Thecontroller150 is then configured to control740 the pitch of theaircraft1, specifically by controlling741 the position of thewinglet120, to bring the pitch of theaircraft1 towards the target pitch of theaircraft1. The target pitch of theaircraft1 in this example is a pitch of the aircraft at which a level of drag produced by thefuselage10 is at a minimum. In other words, the target pitch of theaircraft1 is such that thelongitudinal axis15 of the aircraft is aligned with the direction of travel of theaircraft1. In other examples, the target pitch is any other suitable pitch, such as a pitch at which any of the above-listed properties approaches, or reaches, a respective target value, or a theoretical pitch at which a property (such as fuel consumption, efficiency, and/or drag of the aircraft) is improved or optimised. In other examples, thecontroller150 is configured to control740 the attitude of theaircraft1 so as to influence or control one or more of the properties listed above, such as to bring one or more of the above listed properties towards a respective target value. For instance, thecontroller150 may be configured to control740 the attitude, such as the pitch, of theaircraft1 to facilitate maintenance of a target fuel consumption, target efficiency, and/or a target drag of theaircraft1.

Thecontroller150 in the present example is configured to control740 the attitude of theaircraft1 in particular during a cruise phase of a flight of theaircraft1. This can improve an efficiency of theaircraft1 as fuel is consumed and the attitude of theaircraft1 changes throughout the cruise phase, for example without, or in addition to, using a fuel ballast system to control a centre ofgravity13 of theaircraft1. In some examples, thecontroller150 is alternatively, or in addition, configured to control740 the attitude of theaircraft1 during a take-off and/or a landing procedure of theaircraft1. Alternatively, thecontroller150 may control the position of thewinglet120 during a take-off and/or landing procedure, such as to reduce a separation of airflow over thewinglet120 and thereby improve a lift generated by thewing system100. This may allow theaircraft1 to take-off and/or land at slower speeds and/or have a reduced landing and/or take-off distance than may otherwise be possible. This may allow theaircraft1 to land at airports having shorter runways than would otherwise be possible. Thecontroller150 is configured to move740 thewinglet120 to the stowed position S, such as after a flight when theaircraft1 is performing ground manoeuvres. Thecontroller150 is also configured to move750 thewinglet120 from the stowed position S to the extended position Z and/or any suitable deflected position A, B, such as before a flight of theaircraft1.

Turning now toFIG.6, thewing system100 of the present example comprises a restrictor600 that is operable to restrict a range of movement of thewinglet120 relative to thewing portion110. Therestrictor600 comprises abody610 that is fixed to thewing portion110, and aslot620 within which a portion of thewinglet120, which is here aprotrusion630 of thewinglet120, is configured to move. Theslot620 as a fixed dimension, which is here an arc, along which theprotrusion630 can move as the position of thewinglet120 is controlled or varied, thereby restricting a range of movement of thewinglet120. Therestrictor600 is releasable from theprotrusion630 to disengage therestrictor600. This is here by thebody610 being movable relative to thewinglet120 and theprotrusion630, specifically by thebody610 being rotatable about apivot axis650 to disengage theprotrusion630 from theslot620. In other examples, theprotrusion630 is movable relative to thebody610 and/or theslot620 to disengage theprotrusion630 from theslot620. It will be appreciated that the restrictor600 shown and described with reference toFIG.6 is merely an illustrative example, and therestrictor600 may be configured to restrict a range of movement of thewinglet120 in any other suitable way. For instance, in other examples, a length of theslot620 may be variable so as to vary a level of restriction of movement of thewinglet120 provided by therestrictor600.

Therestrictor600 is operable by thecontroller150. Specifically, thecontroller150 is configured to selectively engage715 or disengage745 therestrictor600. The restrictor600 inFIG.6 is shown in an engaged configuration, in which theslot620 is engaged with theprotrusion630 of thewinglet120. Thewinglet120 is shown in two different positions at opposing extremes of the range of movement permitted by therestrictor600. As noted above, in the engaged configuration, the range of movement of thewinglet120 is restricted by a length of an arc formed by theslot620. In this case, the range of movement of thewinglet120 is restricted to a rotation of 10° above and below the extended position Z of thewinglet120, but in other examples may be any other suitable range, such as up to 5°, up to 10°, up to 15°, up to 20°, up to 25°, up to 30°, or greater than 30° from the extended position Z, in one or both directions. Therestrictor600 may be disengaged, such as by moving thebody610 comprising theslot620 relative to thewing portion110 and theprotrusion630, as described above.

When thewinglet120 is in the stowed position S before a flight, the controller is in the present example configured to move710 thewinglet120 from the stowed position S, such as to the extended position Z and/or any suitable deflected position A, B. Thecontroller150 is additionally configured to engage715 the restrictor600 before and/or during a flight of theaircraft1, such as to permit the position of thewinglet120 to be varied within a restricted range during the flight. The flight may include a take-off and landing procedure of theaircraft1, as well as a cruise phase of theaircraft1. Thecontroller150 is also configured to disengage745 the restrictor600 when theaircraft1 is on the ground, such as after a flight when theaircraft1 is performing ground manoeuvres and/or when theaircraft1 is in proximity to a boarding terminal of an airport. In this way, thecontroller150 is able to move750 thewinglet120 to the stowed position S described above when theaircraft1 is on the ground. Although not shown here, therestrictor600 may comprise a mechanism for locking thewinglet120 in the stowed position S, such as a pin, biasing means, or any other suitable mechanism. Alternatively, or in addition, thewing system100 may comprise a lock, other than the restrictor600, for holding thewinglet120 in the stowed position S. In some such examples, thecontroller150 is configured to selectively engage and disengage the lock and/or the mechanism of the restrictor600 to respectively hold thewinglet120 in the stowed position S and release the winglet from the stowed position S.

FIG.8 shows a schematic diagram of a non-transitory computer-readable storage medium800 according to an example. The non-transitory computer-readable storage medium800

stores instructions

830 that, if executed by aprocessor820 of acontroller810, cause theprocessor820 to perform a method according to an example. In some examples, thecontroller810 is thecontroller150 as described above. Theinstructions830 comprise: obtaining631 information representative of the attitude of theaircraft1; and, on the basis of the information, controlling the attitude of theaircraft1 by controlling a position of thewinglet120 relative to thewing portion110, thereby to control an angle of incidence of thewinglet120. In other examples, the instructions330 comprise instructions to perform any other example methods described herein, such as themethod700 described above with reference toFIG.7.

It will be understood that thewing system100,controller150,aircraft1,method700 and non-transitory computer-readable storage medium800 described above are illustrative examples only. Variations and/or modifications can be made within the scope of the invention as defined by the appended claims. For instance, some examples may not comprise therestrictor600. In other examples, thewinglet120 may not be movable to the stowed position S, or thewinglet120 may be movable above the extended position Z to a different extent than thewinglet120 is movable below the extended position Z. Other variations and modifications will be foreseeable to the skilled person.

It is to be noted that the term “or” as used herein is to be interpreted to mean “and/or”, unless expressly stated otherwise.

Claims

1. An aircraft attitude controller configured to:

obtain information representative of an attitude of an aircraft; and,

on the basis of the information, control the attitude of the aircraft by actively controlling a position of a winglet at a distal end of a wing portion of a wing of the aircraft, relative to the wing portion, thereby to control an angle of incidence of the winglet.

2. The aircraft attitude controller ofclaim 1, wherein the attitude of the aircraft comprises a pitch of the aircraft and/or an angle of attack of the aircraft.

3. The aircraft attitude controller ofclaim 1, wherein the information comprises information on any one or more of the following properties:

a pitch of the aircraft;

an angle of attack of the aircraft;

a speed of the aircraft;

a drag of the aircraft;

a mass of the aircraft;

a distribution of mass of the aircraft;

a centre of gravity of the aircraft;

an amount of fuel in the aircraft;

a fuel consumption of the aircraft; and

an efficiency of the aircraft.

4. The aircraft attitude controller ofclaim 1, configured to determine a target attitude of the aircraft,

wherein the controlling the attitude of the aircraft comprises controlling the attitude of the aircraft to bring the attitude of the aircraft towards the target attitude of the aircraft.

5. A wing system for an aircraft, the wing system comprising at least a wing portion of a wing, a winglet at a distal end of the wing portion, and a controller, wherein a position of the winglet relative to the wing portion is variable to change an angle of incidence of the winglet, and

wherein the controller is configured to obtain information representative of an attitude of an aircraft, and, on the basis of the information, to control the attitude of the aircraft by actively controlling the position of the winglet relative to the wing portion.

6. The wing system ofclaim 5, wherein the winglet is rotatably movable relative to the wing portion.

7. The wing system ofclaim 6, wherein an axis of rotation of the winglet relative to the wing portion is orientated at a non-zero toe angle to a vertical plane that includes a longitudinal axis of the aircraft.

8. The wing system ofclaim 5, comprising a restrictor operable to restrict a range of movement of the winglet.

9. The wing system ofclaim 5, wherein the winglet is movable to an extended position, in which a proximal end of the winglet is substantially aligned with the distal end of the wing portion, and

wherein a span of the winglet, when the winglet is in the extended position, constitutes from 10% to 50% of the total span of the wing comprising the wing portion.

10. The wing system ofclaim 5, comprising an actuator for varying the position of the winglet relative to the wing portion.

11. The wing system ofclaim 5, wherein the attitude controller is configured to:

obtain information representative of an attitude of an aircraft; and,

12. A method of controlling an attitude of an aircraft, the method comprising:

obtaining information representative of the attitude of the aircraft; and,

on the basis of the information, controlling the attitude of the aircraft by controlling a position of a winglet at a distal end of a wing portion of a wing of the aircraft, relative to the wing portion, thereby to control an angle of incidence of the winglet.

13. The method ofclaim 12, comprising determining a target attitude of the aircraft,

14. A non-transitory computer-readable storage medium storing instructions that, when executed by a processor, cause the processor to perform the method ofclaim 12.

15. An aircraft comprising the controller ofclaim 1.

16. An aircraft comprising the wing system ofclaim 5.

17. An aircraft comprising the non-transitory computer-readable storage medium ofclaim 14.